This invention relates to methods and apparatus for sealing a flexible bag, preferably a five-sided plastic bag, to a pallet having plastic sheeting at its periphery. Such pallets are used to hold and to convey containers of fresh produce such as strawberries from one location to another.
The methods and apparatus of this invention are improvements over the methods and apparatus disclosed in the following, issued U.S. Pat. Nos. 5,046,302; 5,014,495; and 4,821,489. The disclosures including the drawings of these patents are incorporated herein by reference as though fully set forth here.
These three issued U.S. patents describe systems that include a rotatable turntable and a single pressure roller to apply tape to bagged pallets of fresh produce to seal a five-sided plastic bag over a square pallet with plastic sheeting at its periphery and produce such as strawberries atop the pallet. These systems are less effective in sealing such a plastic bag to a rectangular or oblong pallet.
This invention provides a new system comprising a rotatable turntable, preferably, but not necessarily including, a plurality of pressure rollers to apply tape and to seal a five-sided, open-ended plastic bag to a pallet bearing produce and having plastic sheeting at its periphery, at a minimum, or over the pallet""s upper surface and at its periphery. The rotatable turntable has an upper support surface to carry and support such a pallet. The pallet itself may be square, rectangular, oblong, or have a plurality of sides of equal or unequal length.
The system also includes an adhesive tape dispenser disposed in operative relationship to the rotatable turntable. The dispenser applies tape from a single roll of tape or a plurality (e.g. two) of rolls to seal a five-sided plastic bag to plastic sheeting at the periphery of the pallet, thus sealing the plastic bag to the plastic sheeting and to the pallet.
The system may include a pressure roller system comprising four rotatable rollers rotatably mounted on a single rotatable carrier. This carrier is operatively adapted to apply pressure against, and to seal the tape, substantially continuously, to the sheeting at the periphery of the pallet and to the edges at the open-end of the plastic bag that overlap the sheeting.
The pressure roller system is mounted for movement of the first and the second of the four rollers into engagement with the tape, the sheeting at the periphery of the pallet, and the plastic bag, during rotation of the turntable, and for rotation of the carrier during rotation of the turntable to bring one or more of the other rollers, i.e. the third of fourth rollers, into engagement with the edges of the pallet, sheeting, tape and bag during rotation of the turntable and to move the first roller, the second roller, or both, out of such engagement. For example, when a first roller meets an obstruction, and stalls, the roller assembly pivots around the stalled roller. Once the next roller in sequence contacts the surface to be sealed, pressure applied by the new roller, now the lead roller at the surface to be sealed, allows the following roller to overcome the obstruction and to continue on, applying pressure, but now as the following roller. This reference is as follows in summary:
A) A lead roller hits an obstruction and stalls;
B) The roller assembly flips or pivots on stalled lead roller;
C) Once roller assembly has flipped or rotated 90xc2x0, a new lead roller is established; and
D) The former lead roller is now a following roller.
In preferred embodiments, the four rotatable rollers are mounted at the corners of a square array, and are carried on an adjustable, fluid e.g. air pressure-driven arm that moves the roller system into engagement with the adhesive tape, the edges of the sheeting and the plastic bag where the open edges of the plastic bag overlap the sheeting attached to the pallet. Thus, two of these four rotatable rollers apply pressure against, and seal such tape, substantially continuously, to the sheeting at the periphery of the pallet, and to the edges of the open end of a plastic bag that overlaps the sheeting, even when the rollers pass around the corners of a pallet.
In practice, for example, the first roller and the second roller may first engage the tape, the sheeting at the periphery of the pallet and the plastic bag, during rotation of the turntable. If the leading edge of the first roller, for example, encounters an obstruction or imperfection, formed for example by produce packages on such a pallet, the rotatable carrier turns, momentarily disengaging the second roller, and then turns, or flips, so that the first and fourth rollers, or the fourth and third rollers, engage the tape, the sheeting at the periphery of the pallet and the plastic bag, thereby renewing continuous application and pressure against them. Such flipping or turning or pivoting around the lead roller may occur at any time such an obstruction is encountered.
The methods of the invention comprise sealing an open-ended, five-sided plastic bag to plastic sheeting attached at the periphery of a pallet to provide a gas-tight container for respiring perishables placed on the pallet. The method includes the steps of placing plastic sheeting on the pallet, or at the periphery of the pallet, preferably with the sheeting edges extending over the periphery of the pallet; positioning an open plastic bag above the pallet, and over produce resting on the pallet, with the bag""s open end margins lying adjacent (i.e. over or under) the plastic sheeting edges; applying adhesive tape simultaneously to the area where the plastic sheeting, and the ends of the plastic bag lie adjacent one another; and rotating the pallet, plastic bag and sheeting to apply such tape, substantially continuously, to seal the bag to the sheeting and thus to the pallet, by maintaining substantially continuous pressure contact of two rollers to the tape during tape application to the plastic bag and plastic sheeting.
In preferred embodiments, the methods of the invention comprise selecting a multi-sided e.g. a rectangular or oblong pallet whose length is at least ten percent greater than its width; placing perishables on the pallet; placing a plastic bag over the perishables such that the open edges of the plastic bag lie over or under plastic sheeting at or over the periphery of the pallet; placing the pallet assembly onto a rotatable turntable; and rotating the turntable while applying the tape to seal the plastic bag to the plastic sheeting, by maintaining contact of two or more pressure rollers to the tape during application of the tape to the bag and sheeting.